Etching Method and Etching Device

ABSTRACT

Disclosed is a dry etching method for etching a metal film on a substrate with the use of an etching gas, wherein the etching gas contains a β-diketone and first and second additive gases; wherein the metal film contains a metal element capable of forming a complex with the β-diketone; wherein the first additive gas is at least one kind of gas selected from the group consisting of NO, NO 2 , O 2  and O 3 ; wherein the second additive gas is at least one kind of gas selected from the group consisting of H 2 O and H 2 O 2 ; wherein the amount of the β-diketone contained is 10 vol % to 90 vol % relative to the etching gas; and wherein the amount of the second additive gas contained is 0.1 vol % to 15 vol % relative to the etching gas. The etching rate of the metal film is increased by this etching method.

FIELD OF THE INVENTION

The present invention relates to a technique for etching a metal filmwith the use of an etching gas containing a β-diketone.

BACKGROUND ART

The manufacturing process of semiconductor devices sometimes includesetching metal films formed on substrates to be used as wiring materials,metal gate materials, electrode materials or magnetic materials.

With the fine processing of semiconductor devices, there has been ademand to highly control the etching of metal films for the purpose ofetching the metal films into a fine structures. More specifically,researches have been made to etch the metal film with etching depthvariations of 1 nm or less in the wafer plane, to control the surfaceroughness of the metal film after the etching, to selectively etch themetal film, and the like. It is however difficult to perform such highetching control by a wet etching method in which a metal film is etchedwith a chemical solution. A dry etching method in which a metal film isetched with a gas is being studied for high etching control.

For example, Patent Document 1 discloses an etching method whichincludes an etching step of etching a thin film on a substrate with anetching gas containing a β-diketone with at least one of water andalcohol, under a condition that the temperature of the substrate is 300°C. or higher, preferably 450° C. or higher, thereby exposing a surfaceof the substrate. Further, Patent Document 2 discloses an etching methodfor etching a metal film by using an etching gas containing a β-diketoneand 1 to 20 vol % of water or hydrogen peroxide and forming a complex ofthe β-diketone and the metal element of the metal film in a temperaturerange of 100° C. to 350° C. In Patent Document 2, zinc, cobalt, hafnium,iron, manganese, vanadium and the like are described as examples of themetal element of the metal film. It is reported in Patent Document 2that the etching rate of the metal film becomes higher with the additionof water or hydrogen peroxide than with the use of oxygen.

The use of β-diketones has also been proposed, not for fine etching ofmetal films formed on substrates, but for dry cleaning of metal filmsdeposited in film-forming apparatuses in semiconductor manufacturingprocess.

For example, Patent Document 3 discloses a dry cleaning method forremoving a metal film deposited in a film-forming apparatus by reactingthe metal film with a cleaning gas containing a β-diketone and NOx(either one of NO and N₂O) in a temperature range of 200 to 400° C.,preferably 250 to 370° C. In Patent Document 3, nickel, manganese, iron,cobalt and the like are described as examples of the constituent metalelement of the metal film in Patent Document 3. It is reported in PatentDocument 3 that the temperature range in which the metal film can beetched and removed becomes wider with the use of NOx than with the useof oxygen.

PRIOR ART DOCUMENTS Patent Documents

-   Patent Document 1: Japanese Laid-Open Patent Publication No.    2004-91829-   Patent Document 2: Japanese Laid-Open Patent Publication No.    2014-236096-   Patent Document 3: Japanese Laid-Open Patent Publication No.    2013-194307

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

It is conceivable that the cleaning gas of Patent Document 3, whichcontains a β-diketone and NOx (either one of NO and N₂O), could be usedas an etching gas for etching a metal film. It has however been found asa result of researches made by the present inventors that, in the caseof etching a metal film on a substrate by supplying a β-diketone to thesubstrate, there is a problem of decomposition of the β-diketone underthe catalytic action of the metal whereby a film predominantly composedof carbon (hereinafter referred to as “carbon film”) remains on thesubstrate after the etching, or a problem of damage to the structure ofa semiconductor device as the workpiece. It has also been found by thepresent inventors that, in the case of using NOx gas as an additive gas,it is possible to suppress the formation of a carbon film and theoccurrence of damage to the workpiece by decreasing the temperature ofthe substrate during the etching. In such a case, however, there is aproblem that the etching rate of the metal film is decreased withdecrease in substrate temperature.

The present invention has been made in view of the above circumstances.It is an object of the present invention to provide a method for etchinga metal film at an improved etching rate.

Means for Solving the Problems

The present inventors have found that, in the case of etching a metalfilm with the use of a β-diketone, the etching rate of the metal film isincreased with the addition of not only an oxidizing gas such as NO butalso water etc. to the β-diketone. The present invention is based onthis finding.

According to one aspect of the present invention, there is provided adry etching method comprising etching a metal film on a substrate bybringing an etching gas into contact with the metal film in atemperature range of 100° C. to 350° C., wherein the etching gascontains a β-diketone, a first additive gas and a second additive gas;wherein the metal film contains a metal capable of forming a complexwith the β-diketone; wherein the first additive gas is at least one kindof gas selected from the group consisting of NO, NO₂, O₂ and O₃; whereinthe second additive gas is at least one kind of gas selected from thegroup consisting of H₂O and H₂O₂; wherein the amount of the β-diketonecontained in the etching gas is 10 vol % to 90 vol % relative to thetotal amount of the etching gas; and wherein the amount of the secondadditive gas contained in the etching gas is 0.1 vol % to 15 vol %relative to the total amount of the etching gas.

It is possible by the etching method according to the present inventionto increase the etching rate of the metal film.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of an etching device according to oneembodiment of the present invention.

FIG. 2 is a schematic cross-sectional view of a filled containeraccording to one embodiment of the present invention.

FIG. 3 is a graph showing the relationship between the amount of waterin the etching gas and the rate of etching by the etching gas in Exampleand Comparative Example.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, embodiments of the present invention will be described indetail below. It should be understood that: the present invention is notlimited to the following embodiments; and various changes andmodifications of the following embodiments can be made as appropriatewithout departing from the scope of the present invention.

(Etching Method of Metal Film)

One embodiment of the present invention is a dry etching method foretching a metal film on a substrate with the use of an etching gas,wherein the etching gas contains a β-diketone, a first additive gas anda second additive gas; and wherein the metal film contains a metalelement capable of forming a complex with the β-diketone.

When the etching gas is introduced into an etching device in which theworkpiece with the metal film is placed, and then, brought into contactwith the metal film of the workpiece under heating, a metal complex isformed by reaction of the β-diketone with the metal element of the metalfilm. Since the metal complex is high in vapor pressure, the metal filmis removed by vaporization of the metal complex. The present inventionis characterized in that the etching rate of the metal film is increasedwith the addition of the first and second additive gas into the etchinggas.

It is assumed that, in the present invention, the etching rate isincreased because: the first additive gas added has oxidizing abilityand thus can oxide the metal film; and the second additive gas added canform the metal complex by being bonded to the β-diketone and to themetal element of the metal film.

In the present invention, the etching rate is determined as the amountof decrease of the thickness of the metal film per unit time (in unitsof nm/min) based on a difference in weight (i.e. weight change) of theworkpiece before and after etching treatment and a specific gravity ofthe metal film.

The metal film, as the etching target to be processed by the dry etchingmethod in the present invention, contains a metal element capable offorming a complex with the β-diketone as mentioned above. The metalelement can be at least one kind of element selected from the groupconsisting of Co, Fe, Ni, Zn, Hf, V and Cu. The metal film can be a filmcomposed of only one of the above-mentioned elements or can be a filmcomposed of two or more elements including any of the above-mentionedelements. Examples of the metal film are those made of metal compounds,such as NiSi, CoSi, HfSi, NiCo, FeCo, CoPt, MnZn, NiZn, CuZn and FeNi,and oxides thereof. The present invention is particularly effective foretching of the metal film containing Co. In the present invention, thesubstrate can be a known semiconductor substrate, glass substrate or thelike.

The first additive gas is at least one kind of gas selected from thegroup consisting of NO, NO₂, O₂ and O₃. The second additive gas is atleast one kind of gas selected from the group consisting of H₂O andH₂O₂.

Examples of the β-diketone usable in the present invention arehexafluoroacetylacetone, trifluoroacetylacetone and acetylacetone. Theβ-diketone can be of one kind or of two or more kinds in combination.For high-rate etching, hexafluoroacetylacetone andtrifluoroacetylacetone are preferred. The etching rate of the metal filmis increased with increase in the concentration of the β-diketonecontained in the etching gas. In the case where the vapor pressure ofthe β-diketone is so low that there is a possibility of liquefaction ofthe β-diketone in a film forming apparatus, however, it is preferable toadjust the concentration of the β-diketone in the etching gas with theaddition of a diluent gas.

From the viewpoint of attaining a sufficient etching rate, the amount ofthe β-diketone contained in the etching gas is preferably 10 vol % to 90vol %, more preferably 30 vol % to 60%, relative to the etching gascomposition.

From the viewpoint of attaining a sufficient etching rate, the amount ofthe first additive gas contained in the etching gas is preferably 0.01vol % to 10 vol %, more preferably 0.05 vol % to 8 vol %, still morepreferably 0.1 vol % to 5 vol %, relative to the etching gascomposition.

Further, the amount of the second additive gas contained in the etchinggas is generally 0.1 vol % to 15 vol %, preferably 0.5 vol % to 10 vol%, more preferably 2 vol % to 8 mass%, relative to the etching gascomposition. The content rate of the second additive gas to theβ-diketone in the etching rate is preferably 0.5 vol % to 50 vol %, morepreferably 1 vol % to 20 vol %.

The etching gas may contain an inert gas such as N₂, He, Ar, Ne, Kr orthe like in addition to the β-diketone and the first and second additivegases. As long as the etching gas is diluted to an appropriateconcentration with the addition of the inert gas, there is no particularlimitation on the amount of the inert gas contained in the etching gas.The amount of the inert gas contained in the etching gas is generally 1vol % to 90 vol %, preferably 10 vol % to 80 vol %, more preferably 30vol % to 50 vol %, relative to the etching gas composition.

(Etching Device)

The dry etching method according to the present invention can beembodied in an ordinary etching device for semiconductor manufacturingprocess as shown in FIG. 1. More specifically, one embodiment of thepresent invention is an etching device 100 including: a treatmentchamber 110 in which the substrate (as a workpiece 112) with the metalfilm containing a metal element capable of forming a complex with theβ-diketone is placed; a β-diketone supply unit 130 connected to thetreatment chamber 110 and configured to supply the β-diketone; a firstadditive gas supply unit 140 connected to the treatment chamber 110 andconfigured to supply the first additive gas; a second additive gassupply unit 150 connected to the treatment chamber 110 and configured tosupply the second additive gas; an inert gas supply unit 160 connectedto the treatment chamber 110 and configured to supply the inert gas; aheating unit 170 configured to heat the treatment chamber 110; and acontrol unit (not shown) connected to the β-diketone supply unit 130,the first additive gas supply unit 140, the second additive gas supplyunit 150 and the like and configured to output control signals tocontrol valves to supply the β-diketone and the other gases to theworkpiece 112.

The treatment chamber 110 includes therein a placement stage 111 onwhich the workpiece 112 is placed. There is no particular limitation onthe treatment chamber 110 as long as the treatment chamber 110 isresistant to the β-diketone used and is capable of being evacuated to apredetermined pressure level. In general, an ordinary treatment chamberof a semiconductor etching device can be utilized as the treatmentchamber 110. There is also no particular limitation on the pipes forsupply of the etching gas and the other pipes as long as these pipes areresistant to the β-diketone used. Ordinary pipes can be utilized.

The β-diketone supply unit 130 is connected to the treatment chamber110. The β-diketone is supplied from the β-diketone supply unit 130 intothe treatment chamber 110 through the pipe 121. As shown in FIG. 1, theβ-diketone supply unit 130 is equipped with a valve 135 and a flow rateregulator 133 so as to regulate the amount of the β-diketone supplied.The regulated amount of the β-diketone is fed from the pipe 131 to intothe pipe 121. Further, the inert gas supply unit 160 is equipped with avalve 165 and a flow rate regulator 163 so as to regulate the amount ofthe inert gas supplied as the diluent gas. The regulated amount of theinert gas is fed from the pipe 161 into the pipe 121. The first additivegas supply unit 140 is equipped with a valve 145 and a flow rateregulator 143 so as to regulate the amount of the first additive gassupplied. The regulated amount of the first additive gas is fed from thepipe 141 into the pipe 121. The second additive gas supply unit 150 isequipped with a valve 155 and a flow rate regulator 153 to regulate theamount of the second additive gas supplied. The regulated amount of thesecond additive gas is fed from the pipe 151 into the pipe 121.

It is preferable in the etching device 100 that the β-diketone issupplied in a state of being diluted to a predetermined concentrationwith the inert gas supplied from the inert gas supply unit 160 and beingmixed at a predetermined concentration with the first and secondadditive gases supplied from the first and second additive gas supplyunits 140 and 150. The β-diketone may however not necessarily be dilutedwith the inert gas.

The heating unit 170 is disposed externally of the treatment chamber 110so as to heat the treatment chamber 110. As a second heating unit, aheater (not shown) may be disposed inside the placement stage 111. Inthe case where the treatment chamber 110 has a plurality of placementstages, heaters may be provided in the respective placement stages so asto individually set the temperatures of the placement stages topredetermined degrees.

A gas discharge unit for discharge of the gas after the reaction isdisposed on one side of the treatment chamber 110. The discharge gasunit has a vacuum pump 173 by which the gas after the reaction isdischarged from the treatment chamber 110 through the pipe 171 a. Thegas after the reaction is collected in a liquid nitrogen trap 175 whichis disposed between the pipes 171 a and 171 b. Valves 177 a and 177 bare disposed between the pipes 171 a and 171 b so as to regulate thepressure of the gas. In FIG. 1, PI 123 and PI 125 are pressure gauges.Base on the readings of these pressure gauges, the respective flow rateregulators and valves are controlled by the control unit.

An implementation example of the etching method by the etching device100 will be now explained below.

The substrate (workpiece 112) with the metal film containing a metalelement capable of forming a complex with the β-diketone is placed inposition. The insides of the treatment chamber 110, the pipes 121, 131,141, 151 and 161, the liquid nitrogen trap 175 and the pipes 171 a and171 b are evacuated to a predetermined pressure level by the vacuum pump173. After that, the workpiece 112 is heated by the heating unit 170.When the temperature of the workpiece 112 reaches a predetermineddegree, the β-diketone, the first and second additive gases and thediluent gas are respectively supplied at predetermined flow rates fromthe β-diketone supply unit 130, the first and second additive gas supplyunits 140 and 150 and the inert gas supply unit 160 into the pipe 121.

The β-diketone is diluted and then mixed at a predetermined compositionratio with the additive gases. The thus-mixed etching gas is suppliedinto the treatment chamber 110. While introducing the mixed etching gasinto the treatment chamber 110, the pressure inside treatment chamber110 is controlled to a predetermined pressure level. Then, the metalfilm is subjected to etching treatment by reacting the metal film withthe etching gas for a predetermined time. In the present invention, theetching treatment enables plasmaless etching. There is thus no need toexcite the etching gas into a plasma during the etching treatment.

After the completion of the etching treatment, the heating operation ofthe heating unit 170 is stopped so that the workpiece is cooled; and theevacuating operation of the vacuum pump 173 is stopped so that thevacuum inside the treatment chamber and the like is released. Asexplained above, the metal film is etched by the etching methodaccording to the present invention.

(Etching Conditions)

In the etching method according to the present invention, the etchingtreatment is performed at any temperature where the complex can bevaporized. In particular, the temperature of the etching target metalfilm during the etching treatment is preferably in a range of 100° C. to350° C., more preferably higher than or equal to 150° C. and lower than250° C. There is no particular limitation on the pressure inside thetreatment chamber during the etching treatment. The pressure inside thetreatment chamber during the etching treatment is generally in a rangeof 0.1 kPa to 101.3 kPa.

In the case where: the etching target metal film contains cobalt; andthe etching gas contains hexafluoroacetylacetone as the β-diketone andnitrogen monoxide as the additive gas, the etching of the metal film bythe etching gas at a high temperature of about 300 to 400° C. may resultin a problem of carbon film formation by decomposition of thehexafluoroacetylacetone or a problem of damage to the device structure.In view of these problems, it is preferable that the workpiece is heatedat a temperature higher than or equal to 150° C. and lower than 250° C.,more preferably higher than or equal to 200° C. and lower than 250° C.,still more preferably higher than or equal to 220° C. and lower than250° C. In the above temperature range, the pressure inside thetreatment chamber is preferably set to 20 Torr to 300 Torr (2.67 kPa to39.9 kPa), more preferably 50 Torr to 250 Torr (6.67 kPa to 33.3 kPa),still more preferably 100 Torr to 200 Torr (13.3 kPa to 26.7 kPa), fromthe viewpoint of attaining a sufficient etching rate.

There is no particular limitation on the etching time. In view of theefficiency of the semiconductor manufacturing process, the etching timeis preferably 60 minutes or less. Herein, the etching time refers to atime elapsed from the introduction of the etching gas into the treatmentchamber in which the substrate is placed and subjected to etchingtreatment until the discharge of the etching gas from the treatmentchamber by the vacuum pump etc. for completion of the etching treatment.

(Pretreatment of Workpiece)

Pretreatment may be performed on the workpiece as required. In the casewhere the etching target metal film contains cobalt, for example,etching rate variations depending on the thickness of the metal film areimproved by reducing natural cobalt oxide.

It is feasible to perform the pretreatment by e.g. supplying a reducinggas to the workpiece 112 from a reducing gas supply unit (not shown).

In this reducing gas supply step, the reducing gas supplied can be, butis not limited to, hydrogen gas. Gas of carbon monoxide (CO),formaldehyde (HCHO) or the like can also be used as the reducing gas.

Although the reducing gas such as hydrogen gas can be supplied solely inthe reducing gas supply step, it is preferable to dilute the reducinggas with a diluent gas such as nitrogen gas.

It is further preferable that the β-diketone and nitrogen monoxide gasare not supplied in the reducing gas supply step. More specifically, theamount of the β-diketone and nitrogen monoxide gas supplied ispreferably less than 0.01 vol %, more preferably less than 0.001 vol %,still more preferably 0 vol %, relative to the total amount of the gasessupplied in the reducing gas supply step.

There is no particular limitation on the treatment temperature of thereducing gas supply step as long as the treatment temperature is in therange where the natural oxide can be reduced. When the treatmenttemperature of the reducing gas supply step is low, however, thereduction reaction of the natural oxide does not almost proceed.Although the treatment temperature of the reducing gas supply step canbe set high, the treatment temperature of the reducing gas supply stepis preferably equal to the treatment temperature of the first mixed gassupply step from the viewpoint of operation of the etching device. It isconsequently preferable in the reducing gas supply step that theworkpiece is heated to 100° C. to 350° C., more preferably 150° C. to250° C., still more preferably 200° C. to 250° C.

In the reducing gas supply step, the flow rate of the reducing gas isvaried depending on the volume of the treatment chamber. There is noparticular limitation on the pressure inside the treatment chamberduring the reducing gas supply step. The pressure inside the treatmentchamber during the reducing gas supply step is set appropriately withinthe range of e.g. 10 to 500 Torr (1.33 to 66.5 kPa) according to thedevice.

The treatment time of the reducing gas supply step can be adjusted asappropriate depending on the film forming method of the metal film onthe substrate and the like.

(Filled Container)

In the present invention, the β-diketone supply unit 130 can be aβ-diketone filled container 200 having a sealed container body 201filled with a β-diketone as shown in FIG. 2. The β-diketone filledcontainer 200 is obtained by charging the β-diketone in liquid form intothe sealed container body 201. In the sealed container body 201, theβ-diketone is separated into a liquid phase 213 and a vapor phase 211.An outlet port 203 for charging and discharging of the β-diketone isattached to the sealed container body 201 so that the β-diketone in thevapor phase 211 can be supplied in gaseous form from the outlet port. Inthe case of supplying the β-diketone in gaseous form from the β-diketonefilled container 200, it is necessary to heat the β-diketone filledcontainer 200 and compensate for vaporization heat of the β-diketone inthe liquid phase 213.

The β-diketone content (purity) of the β-diketone filled in liquid forminto the sealed container body 201 is preferably 99 mass % or higher,more preferably 99.5 mass % or higher, still more preferably 99.9 mass %or higher. Herein, the β-diketone content (purity) of the β-diketone inliquid form is measured by gas chromatography.

(Semiconductor Device)

The etching method according to the present invention is applicable asan etching method for forming a predetermined pattern on a metal film ofa conventional semiconductor device. The semiconductor device can bemanufactured at low cost with the use of the metal film etched by theetching method according to the present invention. Examples of such asemiconductor device are solar cells, hard disk drives, dynamic randomaccess memories, phase-change memories, ferroelectric random accessmemories, magnetoresistive random access memories, resistive randomaccess memories, MEMS and the like.

EXAMPLES

The embodiments of the present invention will be described in moredetail below by way of the following examples. It should be understoodthat the present invention is not limited to the following examples. Theetching test of metal films was carried out as follows to examine therelationship between the amount of water contained in the etching gasand the etching rate of the metal film by the etching gas.

A β-diketone filled container was obtained by filling a sealed containerbody with liquid hexafluoroacetylacetone (HFAc). Thehexafluoroacetylacetone used had a purity of 99.9 mass % or higher.

The etching device used was of the same type as the etching device 100shown in FIG. 1. As the workpiece 112, a foil of cobalt (with a size of2 cm×2 cm and a thickness of 0.1 mm) was used. The above-obtainedβ-diketone filled container was used as the β-diketone supply unit.

The insides of the treatment chamber 110, the pipes 121, 131, 141, 151and 161, the liquid nitrogen trap 175 and the pipes 171 a and 171 b wereevacuated to a pressure of lower than 10 Pa. The workpiece on theplacement stage 111 was heated by the heating unit 170 and the heaterinside the placement stage 111. Herein, the weight of the workpiece hadpreviously been measured. Upon confirming that the heating unit 170 andthe heater inside the placement stage 111 reached 220° C., the reducinggas supply step was performed as the pretreatment by supplying hydrogengas at a rate of 10 sccm and a pressure of 50 Torr from a hydrogen gassupply unit for 5 minutes. After the completion of the pretreatment, theinsides of the treatment chamber and the like were again evacuated to apressure of lower than 10 Pa. Then, the β-diketone, the first and secondadditive gases and the inert gas were fed at predetermined flow ratesinto the pipe 121 so as to thereby introduce the etching gas into thetreatment chamber 110 while controlling the pressure inside thetreatment chamber 110 to a predetermined pressure level. After the lapseof a predetermined time from the initiation of the introduction of theetching gas, the introduction of the etching gas was stopped; and thevacuum inside the treatment chamber was released. The workpiece wastaken out from the treatment chamber. The weight of the workpiece wasmeasured. The etching rate of the metal film was determined from theamount of decrease of the thickness of the metal film based on a changein the weight of the workpiece before and after the test operation aswell as the etching time.

In the etching test, the temperature of the workpiece was 220° C.; thetotal amount of the etching gas introduced was 100 sccm; the firstadditive gas used was NO; the second additive gas used was H₂O; thediluent gas used was N₂; the pressure inside the treatment chamber was100 Torr; and the etching time was 2.5 minutes.

The etching conditions and etching rates of the respective examples andcomparative example are shown in TABLE 1. Further, the relationshipbetween the amount of water contained in the etching gas and the etchingrate of the metal film by the etching gas is shown in FIG. 3.

TABLE 1 First Second additive additive Diluent β-Diketone gas gas gasWater Flow Flow Flow Flow content Etching Target rate rate rate rateamount rate [nm/ metal Kind [sccm] Kind [sccm] Kind [sccm] Kind [sccm][vol %] min] Example 1 Co HFAc 50 NO 1 H₂O 0.5 N₂ 48.5 0.5 21 Example 2Co HFAc 50 NO 1 H₂O 1 N₂ 48 1 24 Example 3 Co HFAc 50 NO 1 H₂O 2 N₂ 47 238 Example 4 Co HFAc 50 NO 1 H₂O 5 N₂ 44 5 41 Example 5 Co HFAc 50 NO 1H₂O 8 N₂ 41 8 31 Example 6 Co HFAc 50 NO 1 H₂O 10 N₂ 39 10 22Comparative Co HFAc 50 NO 1 H₂O 0 N₂ 49 0 12 Example 1

As is apparent from FIG. 3, the etching rate was 21 nm/min or higher inExamples 1 to 6 in which the second additive gas was contained in theetching gas, and was twice or more higher in Examples 1 to 6 than inComparative Example 1 in which no second additive gas was contained inthe etching gas. The etching rate was particularly high in Examples 3 to5 in which the amount of water contained in the etching gas was 2 to 8vol %. In each of the examples and comparative example, the formation ofa carbon film was not observed because the temperature of the workpiecewas at a low degree of 220° C.

DESCRIPTION OF REFERENCE NUMERALS

-   100: Etching device-   110: Treatment chamber-   111: Placement stage-   112: Workpiece-   121: Pipe-   130: β-Diketone supply unit-   131: Pipe-   133 Flow rate regulator-   135: Valve-   140: First additive gas supply unit-   141: Pipe-   143: Flow rate regulator-   145: Valve-   150: Second additive gas supply unit-   151: Pipe-   153: Flow rate regulator-   155: Valve-   160: Inert gas supply unit-   161: Pipe-   163: Flow rate regulator-   165: Valve-   170: Heating unit-   171 a, 171 b: Pipe-   173: Vacuum pump-   175: Liquid nitrogen trap-   177 a, 177 b: Valve-   200: β-Diketone filled container-   201: Sealed container body-   203: Outlet port-   211: Vapor phase-   213: Liquid phase

1. A dry etching method comprising etching a metal film on a substrateby bringing an etching gas into contact with the metal film in atemperature range of 100° C. to 350° C., wherein the etching gascontains a β-diketone, a first additive gas and a second additive gas,wherein the metal film contains a metal capable of forming a complexwith the β-diketone, wherein the first additive gas is at least one kindof gas selected from the group consisting of NO, NO₂, O₂ and O₃, whereinthe second additive gas is at least one kind of gas selected from thegroup consisting of H₂O and H₂O₂, wherein the amount of the β-diketonecontained in the etching gas is 10 vol % to 90 vol % relative to thetotal amount of the etching gas, and wherein the amount of the secondadditive gas contained in the etching gas is 0.1 vol % to 15 vol %relative to the total amount of the etching gas.
 2. The dry etchingmethod according to claim 1, wherein the etching gas is brought intocontact with the metal film in a temperature range of 150° C. to 250° C.3. The dry etching method according to claim 1, wherein the amount ofthe second additive gas contained in the etching gas is 0.5 vol % to 10vol % relative to the total amount of the etching gas.
 4. The dryetching method according to claim 3, wherein the amount of the secondadditive gas contained in the etching gas is 2 vol % to 8 vol % relativeto the total amount of the etching gas.
 5. The dry etching methodaccording to claim 1, wherein the amount of the second additive gascontained in the etching gas is 0.5 vol % to 50 vol % relative to theamount of the β-diketone contained in the etching gas.
 6. The dryetching method according to claim 1, wherein the first additive gas iscontained in the etching gas in an amount of 0.01 vol % to 10 vol %relative to the total amount of the etching gas.
 7. The dry etchingmethod according to claim 1, wherein the metal element is at least onekind of metal element selected from the group consisting of Co, Fe, Ni,Zn, Hf, V and Cu.
 8. The dry etching method according to any claim 1,wherein the β-diketone is at least one kind of compound selected fromthe group consisting of hexafluoroacetylacetone, trifluoroacetylacetoneand acetylacetone.
 9. The dry etching method according to claim 1,wherein the metal film contains cobalt, wherein the etching gas containshexafluoroacetylacetone as the β-diketone, NO as the first additive gasand H₂O as the second additive gas, wherein the amount of H₂O containedin the etching gas is 0.5 vol % to 10 vol % relative to the total amountof the etching gas, and wherein the etching gas is brought into contactwith the metal film in a temperature range of 150° C. to 250° C.
 10. Thedry etching method according to claim 1, wherein the etching gas furthercontains at least one kind of inert gas selected form the groupconsisting of N₂, Ar, He, Ne and Kr.
 11. The dry etching methodaccording to claim 1, comprising, before the etching, pretreating themetal film on the substrate by supplying a reducing gas.
 12. Amanufacturing method of a semiconductor device, comprising etching ametal film on a substrate by the dry etching method according toclaim
 1. 13. An etching device comprising: a treatment chamber equippedwith a heating function and includes therein a placement stage on whicha workpiece having a metal film on a surface thereof is placed; aβ-diketone supply unit configured to supply a β-diketone to theworkpiece; a first additive gas supply unit configured to supply atleast one kind of gas selected from the group consisting of NO, NO₂,O₂and O₃ as a first additive gas to the workpiece; a second additive gassupply unit configured to at least one kind of gas selected from thegroup consisting of H₂O and H₂O₂ as a second additive gas to theworkpiece; and a control unit configured to output control signals to,under a condition that the workpiece is heated in a temperate range of100° C. to 350° C., supply the β-diketone, the first additive gas andthe second additive gas to the workpiece such that the amount of theβ-diketone supplied is 10 vol % to 90 vol % relative to the total amountof the gases supplied to the workpiece such that the amount of thesecond additive gas supplied is 0.1 vol % to 15 vol % relative to thetotal amount of the gases supplied to the workpiece.
 14. The etchingdevice according to claim 13, further comprising: a reducing gas supplyunit configured to supply a reducing gas to the workpiece, wherein thecontrol unit is configured to output control signals to control valvesto supply the reducing gas to the workpiece before supplying theβ-diketone and the first and second additive gases to the workpiece.